Electrical sizing device



Feb. 19, 1935. C. J. GREEN 1,992,027

ELECTRICAh SIZING DEVICE Filed Sept. 5, 1935 WITNESSEG CLARENCE TJ. GREE6M M W Patented Feb. 19,1935

ELECTRICAL SIZING DEVICE Clarence J. Green, Worcester, Mass., asslgnorto Norton Company, Worcester, Mass., a corporation of MassachusettsApplication September 5, 1933, Serial No. 688,128

12 Claims.

This invention relates to work sizing devices and particularly to 'anelectric control mechanism which may be arranged to measure the sizes ofarticles or to regulate the automatic operations of a machine tool, suchas a grinding machine.

As explained in various prior patents, such as the patents to Cady Nos.Re. 17,357 and 1,450,246, it is commonly known that crystals of quartz,tourmaline, and various other materials, when compressed in certaindirections, give positive and negative electrical reactions in variousregions of their surfaces, and this phenomenon is referred to as piezoelectricity.

These piezo electric crystals, when ground in the form of plates andsubjected to alternating electrical fields of high frequencies, tend tovibrate longitudinally, and the frequency of crystal vibrations dependsprincipally upon the thickness of the crystal. Hence, a piezo electriccrystal may .be ground to vibrate at a predetermined frequency.

A rectangular plate of any elastic solid may be struck a sudden blowupon one end and thereby.

set into longitudinal vibration. These mechanically impressed vibrationsare considered free or natural and their frequency depends principallyupon the modulus of elasticity of the material, its densityand itsdimensions. However, if the vibrations on a piezo electric plate areimpressed by the fleld of a high'frequency electric current, they aresaid to be forced and their amplitude of vibrations is extremely minuteexcept when the frequency of the impressed oscillating;

circuit approximates the natural frequency of vibrations of the piezoelectric plate.

A piezo electric crystal, such as quartz-entourmaline, should preferablybe in the shape of aflat, rectangular plate having two opposedsubstantially parallel surfaces, although this is not absolutelynecessary. A quartz crystal has been found to be extremely critical intuning and .will reaclsupon a high frequency circuit at only one givenfrequency or harmonics thereof. It is essential that 'the piezo electriccrystal shall be mounted and connected within an oscillating electricalcircuit in such a manner as to electrically react upon the circuit at aparticular frequency.

If the frequency of the electrically impressed oscillations on a piezoelectric crystal plate is gradually increased from a lesser number ofvibrations per. second than its natural frequency to a slightly greaternumber of vibrations per second than its natural frequency,the'amplitude of crystal vibrations which at first is very small,

will suddenly rise to a large value as the resonant frequency is reachedand as this critical point is passed, it will suddenly fall again to avery small value. Even though these electrically induced crystalvibrations are of themselves so minute as to be hardly detectable, theyare sufficient to exert a very strong reaction upon the electricaloscillating circuit. The current flow in and to an electric oscillatingcircuit having a piezo electric crystal therein is found to sud= 10denly change a maximum extent in strength of flow at a critical pointwhich is at exact crystal resonant frequency.

It has been the usual practice when employing a piezo electric crystalplate, to mount it so that 15 two opposed substantially parallel flatfaces of the piezo crystal are in light frictional contact between twoopposed fiat metal electrically conductive plates acting as terminalstherefor, and connected in an electrical high frequency oscillatingcircuit. However, it has been found that if one of these terminal platesremains in contact with a piezo crystal and the other terminal plate ismoved through a very minute distance towards and from the surface of.the crystal but not in actual contact therewith, the strength ofcurrent flow within and to an electrical. oscillating high frequencycircuit connecting said terminal plates and in exact tuned frequencycircuit connecting said terminal plates and in exact tuned frequencytherewith, is greatly affected.

My invention contemplates the provision of a work sizing device in whichan electric circuit including a piezoelectric crystal and cooperatingelectrically conductive plate is so arranged as to actuate suitablemechanism in accordance with variations in current flow in thecontrolling circuit which-sizes the work and in which the work sizingmechanism may serve to directly indicate the exact size of the workand/or to automatically control the extent of a machining operation as apiece of work is being reduced in size. Broadly considered, the worksizing device serves to indicate the work size whether or. not there isany visible indicator or signal which informs the operator as to thework size.

It is a further object of this invention to employ an electrical worksizing device including a piezo electric crystal arranged to respond tominute reductions in work size during a grinding operation thereon andstop said operation when a desired portion of the work has been reducedto a predetermined size, whereby one may automatically reproduceduplicate work pieces of any given size with extreme accuracy.

With these and other chlccts in vie more ifully apparent in the followherein disclosed and covered. hr claims.

The accompanying drawing diagrammatici illustrates one form i to controlthe size a grinding machine.

[is one speciilc club I have illustrated grin wheel feed mechanism on tnwork sizing device which has a 1' "t including a feelcr memberengageaole Wlbii work and responsive to minute variation in work size.This device employs a piece electric crystal and a plate which arerelatively movable and react within and control the current flow in asensitive thermionic vacuum tube high quency oscillating circuit incritical tune with the natural frequency of the piezo crystal. Thesudden change in current flow within the oscillating circuit is arrangedto operate work size indicating mechanism such as a meter calibratedtoaccurately indicate work size and/or'io operate other electricalmechanisms regulating the ex tent of a grinding operation upon a workpiece so as to reduce said work to a predetermined size within extremelynarrow limits of accuracy. The expression size indicating mechanism" isemployed in the claims to cover any suitable mechanism which may beoperated by or controlled in response to variations in the highfrequency oscillating electric circuit, whether it be a. gauge whichdirectly measures the work size, or whether it be a control mechanismwhich serves to control a machine which operates upon the work, such asis required for reducing its size or for performing any operation neededin connection with taking a measurement of the work size.

As illustrated, the work sizing device is applied to control a grindingmachine wherein a machine base 10 is arranged to slidably support awheel slide 12 for transverse movement thereon so as to feed the wheelinto the work. A grinding wheel 13 is mounted for rotation with a shaft14 journaled within the wheel slide and arranged for movement therewithtowards and from a work piece 15 suitably supported for rotationrelative to the base. If desired, the work piece 15 may be arrangedjorlongitudinal axial movement in any well-known manner such as by a worktable mounted to slide longitudinally of the base'and having a headstockand tallstock thereon arranged to axially support and rotate the work.Since the work support does not constitute a part of my invention andsince it may comprise any familiar construction, it has not beenillustrated.

Any suitable power operated mechanism may be employed to cause a feedingmovement of the grinding wheel 13 and wheel slide 12 relative to thework piece 15. In the present instance, for convenience of illustration,this mechanism comprises a fluid pressure actuated device such as acylinder 1'! integral with the base 10 and having A reversing valve 24is provid -d direction and. extent of mm secured on a t d v lvc stembeing valve cyliir w oi fluid to it. Fluid A source such i ad to thereverse vain into valve chamber 34 between illustrated, fluid may flowur chamber 34 through a passage we] 37 at the right-hand end 01 cylinpiston 18 and cylinder head 38 tend." piston 18 towards the left as indarelative infeed of the grind and into the work. Fluid Within oi theleft-hand end of cylinder 1'? be 18 and cylinder head 21, will exhaust athrough a passage 42 into a chamber 43 betwm valve pistons 27 and 28.Exhaust fluid may i'low from chamber 43 through a pipe 45 into ad.justable throttle valve 46 and thence through pipes 48 and 49 into thefluid supply system indicated by arrows. It will be appreciated that themachine operator'may regulate valve 46 to control the flow of exhaustfluid therethrough and thereby precisely regulate the rate of wheel feedtowards and into the work.

The left-hand end of valve stem 29 is connected to a rod 55 terminatingin a handle 56 conveniently located on the front of the base whereby theoperator may shift the piston positions within the reverse valve tothose indicated in dotted lines and cause fluid flow under pressure fromthe pipe 33 and chamber 34 to enter passage 42 and flow into chamber 40at the lefthand end of cylinder 17 causing a rearward movement of piston18 and a consequent withdrawal of the grinding wheel from the work untilpiston 18 encounters cylinder head 38. During this rearward movement ofpiston 18, fluid will exhaust from chamber 37 through passage 35 intochamber 60 between pistons 25 and 26. The fluid is free to flow fromchamber 60 through pipe 49 back into the supply system. Since the flowof exhaust fluid on the rearward movement of piston 18 is notrestricted, it will be appreciated that the grinding wheel will berapidly withdrawn from the work to its initial starting position asillustrated.

To facilitate an accurate grinding operation wherein work pieces may besuccessively and automatically finished to precisely the same size, Ihave provided an extremely sensitive electrically responsive work sizingdevice which indicates minute variations in work size and serves tooperate the reverse valve and rapidly remove the grinding wheel from thework when the workhas been reduced to a predetermined size. irrespectiveof grinding wheel wear or extent of the wheel feed into the work. Toaccomplish this, I have provided a calipering device 70, arranged toengage the work and measure it during a grinding operation. Thecaliperlng device may be positioned upon the work in any desiredfashion, but is here shown as supported by. means of a bracket 72suitably secured to the grinding wheel guard '73. The caliper mayconsist of any convenient mechanism wherein a fecler member responds tominute variations in work size and serves to move a piezoelectriccrystal and plate relative to each other to control the operation ofother electrical mechanism. In the-present instance, the calipercomprises a casing '75 carrying a slidable feeler rod '76, movable inresponse to variations in work size. The lower end of the casingterminates in an anvil '78 provided with an adjustable contacting screwdiametrically opposed to and aligned with the end of feeler rod '76, andwith another adjustable contact screw 81 arranged to laterally bear uponthe work and maintain the end of the feeler rod and screw 80 in desiredlocations and preferably diametrically of the work whenthe grindingoperation is completed. In. 'oider to reduce the wear of said contactingscrews and the end of the feeler rod engaging the work to aminiconvenient manner so that the weight of the casing '75 and the partsassembled therewith are not supported by feeler rod '76. To accomplishthis, I provide a link 33 which may be clamped in any convenientposition on bracket '72 by means of a screw 84. A link 85 is pivotallyand frictionally supported on link 83 by means of a bolt 86 in suchmanner that said link may be moved about its pivot by the operator butwill remain in the positionto which it is set. The upper end of casing'75 is provided with an L shaped projecting frame 8'7 terminating in anenlarged portion 88 loosely pivoted to link 85 by a pin 89. A spring 91engages pin 89 and an ear 92 on casing '75 under suflicient tension tomaintain screws 80 and 81 in frictional contact with the work, therebysupporting the caliper and providing a free sliding action of the feelerrod '76 therein.

To provide an extremely sensitive work sizing device, the feeler rod 76is arranged to cause a relative movement between a piezo electriccrystal plate and an adjacent metal platewhich members are connected inan electrical oscillatingcircuit in such manner that they control thecurrent flow. therein and thereto. Various piezo electric crystals maybe employed in various ways to control such a. circuit, but I preferablyutilize a rectangular piezo electric crystal plate of quartz orv similarmaterial ground relatively thin to oscillate at a known high frequency.As illustrated, I have provided a piezo electric crystal plate 95secured to a terminal'member 96 which is firmly supported on the frame8'7 but insulated therefrom in any convenient manner as by anonconducting member 9'7. The upper portion of feeler rod "76 isprovided with a fine threaded portion 100 arranged to adjustably supporta member 101 which is movable therewith and prevented from rotarymovement by a slide-way 103 in an upstanding portion 104 of frame 8'7.An upper terminal plate 106 is supported on the underside of member 101directly above and parallel to the flat upper face of the piezo electriccrystal 95. Plate 106 maybe separated from member 101 by a non-conductormember 107.

The caliper frame is further provided with a horizontal projection 110having a hole therein arranged to receive a reducedportion 111 of feelerrod 'lfiiterminat'ing in a knob 112, whereby the threaded portion 100may be turned to adjust the position of plate 108 relative to the topface of the piezo crystal plate 95. To prevent lost motion in thethreaded part and tuming of the feeler rod due to vibration, a spring-114 has been provided which tends to force the feeler rod into flrmfrictional contact with the work, as well asplate 106 toward the crystal95. To prevent damage to the piezo crystal, an adjusting screw 115 isthreaded through the frame and arranged to limit the downward movementof plate 106 before it actually engages the piezo plate 95. It will beappreciated that the illustration has been exaggerated todiagrammatically show the operation of the various parts of my caliperdevice. In actual practice, the plate.106 may be as close to the piezocrystal as one thousandth of an inch, and a movement of said plate 1through one ten thousandth of an inch or less may be sufficient tocontrol the current fiow in the oscillating circuit and effect otherelectrical control mechanisms to measure and/or size the work.

Various types of oscillating electrical circuits may be controlled bythe piezo crystal and plate 106, but I preferably utilize a thermionicvacuum tube of the type used in radio communication and I utilize thevariable flow of electric current in a plate circuit of,-said tube tooperate a miliiammeter which is calibrated in fractions of a thousandthof an inch to indicate variation in work size. I also employ a verysensi tive relay in the plate circuit to make and break contacts in apower circuit operating a solenoid which is arranged to shift thereverse valve 24 and cause a suddenwithdrawal of the grinding wheel 13from engagement with the work and stop the grinding operation when thework has been reduced to a predetermined size.

One circuit which has been found successful is diagrammatically shown inthe drawing. It comprises a thermionic vacuum valve of the familiarthree element type having a filament 121, a grid 122, and a plate 123.The filament or cathode 121 is heated by a batteryl25. An input circuitis provided between the grid 122 and filament 121 which includes aninductance 127 and resistance 129. The piezo electric plate is connectedto the filament 121 and the movable plate 106 is connected to the grid122, thereby subjecting the piezo crystal to the field of an oscillatinghigh frequency electrical circuit. An

output circuit is provided and connected across.

plate 123 and filament 121 of the vacuum tube including inductance 134,choke 135, condenser 136, meters 137 and 138, electromagnet winding ofrelay 140 and a source of potential, such as a battery 141. A variablecondenser 142. is shunted across the inductance 134 and serves to tunethe output tube circuit to any desired frequency. When condenser 142tunes the output circuit to the natural frequency of the piezo electriccrystal plate 95. the valve 120 will oscillate and the piezo crystalwill vibrate at a maximum extent. At' this point, the two valve circuitsare said to be in exact resonance. However. in'the circuit illustrated;it has been found that at the exact point of resonance, there is aminimum current flow in the plate circuit; whereas at a point whereinthe plate circuit is tuned just below resonance, the current flow in theplate circuit is at a maximum and movement of plate 106 toward or fromthe piezo crystal plate 95 through a minute distance, greatly increasesor decreases the current flow in the plate circuit. It is thisphenomenon which has been taken advantage of.

If it is intended to measure the-work directly, either with or withoutcontrolling a grinding operation, the meters 137 and 138 may begraduated to accurately indicate the work size. For example, meter 138may be graduated in thousandths of an inch and meter 137 may becalibrated so that a whole scale reading registers only one thousandthof an inch in the measurement. It will be appreciated that meter 137 ismuch more sensitive than meter'138. To aid in regulating this meter andpreventing a heavy flow of current therethrough, a balancing battery145, a balancing variable resistance 143 and re-- sistance 144 has beenprovided. By regulating the balancing resistance 143, the indicatorneedle of meter 137 may be positioned at the zero point of its scale.This adjustment need be made only when setting up the apparatus or whenchanging from one work size to another. It will thus be apparent thatwhenever the calipering device engages a work piece, the meters 137 and138 will accurately and precisely indicate the exact size of the work. 1

Since an infinitesimal movement of the plate 106 towards the piezoelectric crystal causes a relatively large increase in current flowthrough the output circuit which includes the sensitive relay 140, saidrelay may be regulatedso that it will connect two switch points 146 and147 in a power circuit 150 whenever the meters 137 and 138 indicate 'adesired strength of current flow corresponding with a predetermined worksize. When the switch points 146 and 147 are closed, the current will befree to ilow therethrough from any suitable source and energize asolenoid 152 having an armature 153 slidably mounted therein. Saidarmature may be connected to the valve stem in any suitable manner, oras shown it may comprise an extension of the valve stem. When thesolenoid is energized, the armature 153 will he suddenly drawn therein,causing a reversal of the reverse valve 24 by moving the pistons thereinto the dotted positions shown and resulting in a consequent andinstantaneous withdrawal of the grinding wheel irom the work when thework gauge has indicated a predetermined desired size of work. I

In the operation of my machine, the work piece 15 is inserted ingrinding position and rotated in any suitable manner. Handle 56 is movedby the operator to its full line position as shown, causing a flow offluid pressure irom any suitable source through the reverse valve intocylinder chamber 37 and resulting in an infeed of the grinding wheel asindicated. Adjustment 01. valve 46 in the exhaust system regulates saidrate of infeed of the grinding wheel. The caliper maybe placed on thework at any time prior to the reduction of the work to the desired size.As the work reduces in diameter, the feeler rod 76 will move downwarddue to the action 'of gravity aided by spring 114 until the increase incurrent flow in the plate circuit energizes relay sufficiently toconnect switch points 146 and 147, energizing solenoid 152 and instantlyshifting valve 24 to a reverse position causing a rapid withdrawal ofthe grinding wheel to its initial position. Relay 140 is so adjustedthat it will close the power circuit when meters 137 and 138 indicatethe desired work size. At this point, plate 106 will not have reachedits greatest possible downward travel as limited by screw 115. Uponcompletion of the grinding operation, it is only necessary for themachine operator to replace the finished work piece with a fresh workblank and shift handle 56 to its full line position to again start themachine through its automatic cycle to produce another work piece ofidentical size.

It will be appreciated that my work sizing device may be employed as awork or inspection gauge which accurately and precisely indicates thevariation in thickness or diameter of any work piece as compared to adesired or standard size. For example, my invention could be employed inaccurately measuring precision finished automotive parts such as pistonpins wherein it is desirable to maintain accuracy within one tenthousandths of an inch. In such a device, the construction abovedescribed may be suitably modified to only include the caliper-ingdevice and the input and output circuits. The power circuit 150, relay140 and solenoid 152 would be eliminated. The suitably calibratedmeters'l37 and 138 would directly indicate work size.

It will further be appreciated that my sizing device may be applied toaccurately control the stock removal operation of any machine tool andit is not intended that the invention be limited to the specific exampleillustrated.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. In combination with a work sizing device, a piezo electric crystaland plate which are movable relative to each other in response to minutevariations in work size, a high frequency oscillating electrical circuitincluding thecrystal and plate, said parts being so connected within thecircuit that any relative movement between the crystal and plate servesto vary the current flow without affecting the frequency ofoscillations, and size indicating mechanism .responsive to changes insaid current flow.

2. In combination with a work sizing device, a

piezo electric crystal and plate which are movable relative to eachother in response to minute variations in work size, a high frequencyoscillating electrical circuit including said crystal and plate soarranged that any relative movement between the crystal and plate servesto vary the current flow within the circuit without changing itsfrequency of oscillation, size indicating mechanism for the work sizingdevice which is responsive to variations of current flow within thecircuit, and means operating upon the work which is controlled by saidmechanism.

3. A work sizing device comprising a piezo electric crystal and a platewhich are movable relative to each other, means engageable with the workfor causing said relative movement, a high frequency oscillatingelectrical system having an input circuit including the crystal andplate which are so arranged that any relative movement therebetweenserves to vary the current flow within and to the input circuit and anoutput circuit responsive to current changes in the input circuit andtuned to the approximate resonance of the natural frequency of thecrystal and an electrical device responsive to the current flow in theoutput circuit which measures the work.

4. A work sizing device comprising a piezo electric crystal and a platemovable relative to each other, means engageable with an article to begauged for causing such relative movement as determined by the size ofthe article, an electrical high frequency oscillating system including.tal and plate serves to vary the current flow in the system, andmechanism responsive to the variations in current within the oscillatingsystem which measures the size of said article.

5. A work sizing device comprising a piezo electric crystal and a platemovable relative to each other, a work gauge for causing said relativemovement, an oscillating system employing a thermionic vacuum valvehaving an input circuit including the crystal and plate which are soarranged that any relative movement therebetween acts to vary thecurrent flow of the input circuit, and an output circuit responsive tochanges in the flow of current within the input circuit and tuned to theapproximate resonance of the natural frequency of the crystal, means forreducing the size of the work and an electrical device operated by theoutput circuit which controls the work reducing means and limits thefinal size of the work.

6. A work sizing device comprising work reducing mechanism, a controlmechanism arranged to stop the work reducing operation, a piezo crystaland plate movable relative to each other in response to minutevariations in work size, an oscillative high frequency electricalcircuit including the crystal and plate so arranged that any relativemovement of the crystal and plate serves to vary the current flow in thecircuit, and an electrical device responsive to variations in thecurrent flow within the circuit which is connected to cause said controlmechanism to operate andstop the work reduction when it has reached apredetermined size.

7. A worksiz ing device having a cutting tool movable toward and from awork piece to produce a stock removing operation, said device includinga piezo electric crystal and a plate movable relative to each other inresponse to a change in work size, an oscillating system having an inputcircuit including said crystal and plate, and an output circuitresponsive to changes in the current flow in the input circuit and tunedto substantially the same frequencyas thatof the natural crystal, andelectrical means operated by the output circuit which indicates the worksize dur ing reduction of the work.

8. A machine for reducing the size of a work piece comprisingcontrollable work reducing mechanism, a control mechanism arranged tostop the work reducing operation, a control mechanism therefor includinga piezo electric crystal and plate which are movable relative to eachother in response to a minutevariation in work size, an oscillatingsystem having an input circuit including the crystal and plate which areso arranged that any relative movement therebetween serves to vary thecurrent flow within and to the-input circuit and an output circuitresponsive only to current changes within the input circuit and tuned inapproximate resonance of the natural frequency of the piezo crystal andan electrical mechanism responsive to variation in current flow withinthe output circuit which serves to cause the control mechanism tooperate and stop the work reduction when it has reached a predeterminedsize.

9. A machine tool comprising a cutting tool movable toward and from awork piece to produce a stock removing operation, a piezo electriccrystal and a plate movable relative to each other, a

work engaging member arranged to cause said movement, an oscillatingsystem having an input circuit, including said crystal and plate, and anoutput circuit responsive to variations of current flow in the inputcircuit and tuned in approximate resonance with the natural frequency ofthe crystal, and means responsive toa variation of current flow in theoutput circuit to stop the stock removing operation when the work hasreached a predetermined size.

10. A machine tool comprising a cutting tool movable toward and from awork piece to produce a stock removing operation, a piezo electriccrystal and a plate movable relative to each other in-response to achange in work size, a feeler member engageable with the work andarranged to cause said movement, an oscillating system having an inputcircuit and an output circuit responsive to said input circuit, saidinput circuit including the piezo crystal and plate which is so arrangedthat any relative crystal and plate movement serves to vary the currentflow within the circuit, saidoutput circuit being tuned substantially inresonance with the natural frequency of the piezo crystal, a device inthe output circuit responsive to changes in current flow therein toindicate the work size during a cutting operation thereon, and separatemeans responsive to the current flow in the output circuit to stop thestock removing operation' when the work has reached a predeterminedsize.

11. A grinding machine comprising a rotatable grinding wheel movabletoward and from a work piece, mechanism to feed the wheel into the work,a control device therefor, a piezo electric crystal and a plate movablerelative to each other, means to cause said movement in response to achange in work size, an oscillating system having an input circuitincluding said piezo crystal and plate which'are so arranged that anyrelative movement of the crystal and plate serves to vary the currentflow in said circuits, and an output circuit tuned substantially inresonance with the natural frequency of the crystal and responsive tocurrent fluctuations in the input circuit, and electrical means actuatedby the output circuit arranged to operate the control device and stopthe grinding feed when the work has reached a predetermined size.

12. A grinding machine comprising a rotatable grinding wheel movabletoward and from a work piece, mechanism to feed the wheel into the work,a control device therefor, a piezo electric crystal and plate movablerelative to each other, a work gauge for causing said movement inresponse to a change in work size, an oscillating system having an inputcircuit and an output circuit responsive-to said input circuit, saidinput circuit including'the piezo crystal and plate which are soarranged that any relative crystal and plate movement acts to vary thecurrent flow within the circuit, said output circuit being responsive tocurrent changes in the input circuit and tuned substantially inresonance with the natural frequency of the crystal, means actuated bythe output circuit which indicates the work size and separate mechanismresponsive to the output circuit arranged to terminate the grindingoperation and remove the grinding wheel from the work when it has beenreduced to a predetermined size.

CLARENCE J. GREEN.

